AIM: Exposure to light at night and meal time misaligned with the light/dark (LD) cycle-typical features of daily life in modern 24/7 society-are associated with negative effects on health. To understand the mechanism, we developed a novel protocol of complex chronodisruption (CD) in which we exposed female rats to four weekly cycles consisting of 5-day intervals of constant light and 2-day intervals of food access restricted to the light phase of the 12:12 LD cycle. METHODS: We examined the effects of CD on behavior, estrous cycle, sleep patterns, glucose homeostasis and profiles of clock- and metabolism-related gene expression (using RT qPCR) and liver metabolome and lipidome (using untargeted metabolomic and lipidomic profiling). RESULTS: CD attenuated the rhythmic output of the central clock in the suprachiasmatic nucleus via Prok2 signaling, thereby disrupting locomotor activity, the estrous cycle, sleep patterns, and mutual phase relationship between the central and peripheral clocks. In the periphery, CD abolished Per1,2 expression rhythms in peripheral tissues (liver, pancreas, colon) and worsened glucose homeostasis. In the liver, it impaired the expression of NAD+, lipid, and cholesterol metabolism genes and abolished most of the high-amplitude rhythms of lipids and polar metabolites. Interestingly, CD abolished the circadian rhythm of Cpt1a expression and increased the levels of long-chain acylcarnitines (ACar 18:2, ACar 16:0), indicating enhanced fatty acid oxidation in mitochondria. CONCLUSION: Our data show the widespread effects of CD on metabolism and point to ACars as biomarkers for CD due to misaligned sleep and feeding patterns.

• Keywords
• acylcarnitine, chronodisruption, clock, female, glucose homeostasis, liver, metabolome, pancreas, rat, sleep, suprachiasmatic nucleus,
• MeSH
• Circadian Clocks * physiology   MeSH
• Circadian Rhythm * physiology   MeSH
• Photoperiod MeSH
• Liver * metabolism   MeSH
• Carnitine * analogs & derivatives   metabolism   MeSH
• Rats MeSH
• Metabolome * physiology   MeSH
• Rats, Sprague-Dawley MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• acylcarnitine MeSH Browser
• Carnitine * MeSH

Modification of the Per2 clock gene in mPer2Luc reporter mice significantly alters circadian function. Behavioral period in constant dark is lengthened, and dissociates into two distinct components in constant light. Rhythms exhibit increased bimodality, enhanced phase resetting to light pulses, and altered entrainment to scheduled feeding. Mechanistic mathematical modelling predicts that enhanced protein interactions with the modified mPER2 C-terminus, combined with differential clock regulation among SCN subregions, can account for effects on circadian behavior via increased Per2 transcript and protein stability. PER2::LUC produces greater suppression of CLOCK:BMAL1 E-box activity than PER2. mPer2Luc carries a 72 bp deletion in exon 23 of Per2, and retains a neomycin resistance cassette that affects rhythm amplitude but not period. The results show that mPer2Luc acts as a circadian clock mutation illustrating a need for detailed assessment of potential impacts of c-terminal tags in genetically modified animal models.

• MeSH
• Behavior, Animal MeSH
• Period Circadian Proteins genetics   MeSH
• Circadian Rhythm * MeSH
• Locomotion MeSH
• Luciferases genetics   MeSH
• Mutation MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Feeding Behavior MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Period Circadian Proteins MeSH
• Luciferases MeSH
• Per2 protein, mouse MeSH Browser

The physiological function of the pancreas is controlled by the circadian clock. The aim of this study was to determine whether aging-induced changes in glucose homeostasis affect properties of the circadian clock in the pancreas and/or its sensitivity to disturbances in environmental lighting conditions. mPer2Luc mice aged 24-26 months developed hyperinsulinemic hypoglycaemia, which was likely due to the Pclo-mediated insulin hyper-secretion and Slc2a2-mediated glucose transport impairment in the pancreas, and due to the alterations in Pp1r3c-related glycogen storage and Sgk1-related glucose transport in the liver. In the pancreatic tissue, aging affected clock gene expression only marginally, it upregulated Bmal1 and downregulated Clock expression. Whereas aging significantly impaired the circadian clock in lung explants, which were used as a control tissue, the properties of the pancreatic clock in vitro were not affected. The data suggest a non-circadian role of Bmal1 in changes of pancreatic function that occur during aging. Additionally, the pancreatic clock was more sensitive to exposure of animals to constant light conditions. These findings provide an explanation for the previously demonstrated relationship between disturbances in the circadian system and disordered glucose homeostasis, including diabetes mellitus type 2, in subjects exposed to long-term shift work.

• MeSH
• Circadian Clocks * radiation effects   MeSH
• Period Circadian Proteins metabolism   MeSH
• Glucose metabolism   MeSH
• Homeostasis * MeSH
• Liver metabolism   MeSH
• Colon metabolism   MeSH
• Mice MeSH
• Organ Specificity genetics   MeSH
• Pancreas metabolism   radiation effects   MeSH
• CLOCK Proteins genetics   metabolism   MeSH
• Gene Expression Regulation radiation effects   MeSH
• Aging metabolism   MeSH
• Light MeSH
• ARNTL Transcription Factors genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Bmal1 protein, mouse MeSH Browser
• Period Circadian Proteins MeSH
• Glucose MeSH
• Per2 protein, mouse MeSH Browser
• CLOCK Proteins MeSH
• ARNTL Transcription Factors MeSH